Other than Vin Diesel’s Xander Cage, it hasn’t been revealed yet which characters, if any, from the previous xXx movies will return for xXx 4.
D.J. Caruso previously said that he envisions xXx 4 being about the main protagonists “watching the watchers,” i.e. battling corrupt governments.
The Return of Xander Cage ended with Gibbons faking his death and beginning work on rebuilding the xXx program, and Xander decided to continue with his service.
That would certainly make for a compelling story that marks a new era of the xXx franchise.